JPH0149641B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing expanded graphite, and more specifically, when a raw material pitch is heat-treated,
The present invention relates to a method for producing expanded graphite using carbonaceous mesophase produced in a heat treatment pitch. (Prior Art) Expanded graphite is generally produced by oxidizing graphite and firing it. As the graphite, flaky graphite, which is natural graphite, is used, and it is known that when flaky graphite, which has a particularly developed graphite crystal structure, is used, its volume expands several hundred times due to the above-mentioned treatment. Graphite, which has a structure similar to single crystal graphite, is produced by precipitating carbon excessively contained in molten pig iron, etc. during cooling. Pyrolytic graphite and the like that are precipitated by thermal decomposition are known, and these graphites are also known to expand by the above-mentioned treatment. (Problems to be solved by the invention) However, natural graphite, especially flaky graphite, is mainly produced in uneven locations and its reserves are limited, and natural graphite usually contains ash. If the ash content is high, the expansion coefficient will be low and the formability and quality of the obtained expanded graphite will deteriorate. Natural graphite with low ash content, which does not require any manipulation, is very expensive. When using Kitshu graphite, the crystals contain a large amount of impurities such as iron, and removal of these impurities poses a problem in use, and in the case of pyrolytic graphite, the rate of carbon precipitation and yield are affected. The problem is that it cannot be manufactured in large quantities and at low cost. Furthermore, in the case of so-called artificial graphite, which is obtained by coking the heavy oil obtained as a by-product of the coal or petroleum industry, such as coal tar or residual oil, and then graphitizing it, the raw material coal Tar and petroleum-based residual oils have a small content of impurities such as ash, and when removing ash, they turn into a liquid phase, making the removal process easy, but the degree of development of graphite crystals is different from that of natural graphite. Since it is comparatively small, it hardly expands even if it is subjected to the same oxidation treatment as when using natural graphite, making it impossible to obtain the desired expanded graphite. (Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have determined that the optical anisotropy produced in the raw material pitch by heat treating the raw material pitch is Focusing on the fact that carbonaceous mesophase has pseudographite crystals, by using such carbonaceous mesophase as a raw material for expanded graphite, there is no need for a means for removing ash, etc., and it can be easily produced. They discovered this and arrived at the present invention. That is, an object of the present invention is to provide a method for easily and in large quantities producing expanded graphite, which is a soft graphite useful for producing graphite sheets and the like. This purpose is achieved by heat-treating the raw material pitch at 350 to 500°C to obtain a heat-treated pitch in which carbonaceous mesophase is produced, and then solvent-treating the heat-treated pitch using an organic solvent that does not dissolve the carbonaceous mesophase. , the carbonaceous mesophase is separated and obtained, and the obtained carbonaceous mesophase is heated at 2400℃~
This is achieved by graphitizing in a temperature range of 3100°C and then subjecting the obtained graphitized product to wet oxidation. The present invention will be explained in detail below. As the raw material pitch, coal-based coal tar pitch or petroleum-based pitch, such as pitch from fluidized catalytic cracking by-product tar, direct distillation residue oil of crude oil, pitch from naphtha pyrolysis by-product tar, etc., is used, but preferably. It is best to use coal tar pitch. In addition, these raw material pitches contain a small amount of impurities such as free carbon, so it is best to remove them from the raw materials in advance using a known method, and even use hydrogenated raw material pitches. Good too. Pitch the above raw materials under an inert gas atmosphere for 350 min.
0.5 in the temperature range of ~500℃, preferably 400-450℃
Heat treat for ~20 hours. By this heat treatment, optically anisotropic carbonaceous mesophase is produced in the raw material pitch. The resulting heat-treated pitch containing carbonaceous mesophase is then treated with an organic solvent that dissolves pitch components other than the carbonaceous mesophase but does not dissolve the carbonaceous mesophase, thereby separating and obtaining only the carbonaceous mesophase. As the organic solvent used for separating the carbonaceous mesophase, it is possible to use known organic solvents used in producing mesocarbon microbeads, such as quinoline or mixed oils of aromatic hydrocarbons such as anthracene oil and creosote oil. can. This separation operation is carried out with the aim of removing pitch components other than carbonaceous mesophase as much as possible, and specifically, 0.3 parts by weight or more, preferably 1 part by weight, of an organic solvent is added to 1 part by weight of the heat-treated pitch.
The carbonaceous mesophase is separated and obtained by mixing and stirring at a ratio of ~5 parts by weight. In order to remove pitch components other than the carbonaceous mesophase as much as possible, it is preferable to repeat the above separation operation at least twice. Since pitch itself is a multi-component system of molecules having a complex chemical structure, the amount of pitch dissolved in the solvent depends on the temperature, so it is preferable to separate the carbonaceous mesophase at as high a temperature as possible. Further, hydrogenated carbonaceous mesophase obtained by hydrogenating the obtained carbonaceous mesophase can also be used as the carbonaceous mesophase of the present invention. The carbonaceous mesophase obtained by the above separation procedure is 2400
A graphitized product is obtained by graphitization treatment at a temperature range of .degree. C. to 3100.degree. C., preferably 2800.degree. C. to 3000.degree. The graphitized product is then subjected to a wet oxidation treatment, which can be carried out by a known method, specifically using a mixed acid of sulfuric acid and nitric acid or a peroxyhalogen acid. The oxidation conditions, such as the blending ratio of each acid in the mixed acid of sulfuric acid and nitric acid, treatment time, and treatment temperature, are selected and determined as appropriate. On the other hand, oxidation treatment is carried out using at least the same amount or more for 2 hours or more at 50°C or more. The graphitized carbonaceous mesophase is expanded by the above oxidation treatment to obtain expanded graphite as a product. In the case of natural graphite, it does not expand sufficiently with oxidation treatment, and expands with further heat treatment at approximately 1000°C, but the carbonaceous mesophase of the present invention subjected to graphitization treatment can be further heated after oxidation treatment. There is no particular change in the expansion rate even after the treatment. However, if it is necessary to remove the acidic groups introduced by oxidation treatment, they may be removed by heat treatment. (Effects) According to the present invention, expanded graphite, which is useful as a raw material for producing graphite films, graphite sheets, etc., can be produced at a lower cost and in larger quantities than when natural graphite or the like is used as a starting material. The present invention is industrially very useful. (Examples) Hereinafter, the present invention will be explained in more detail using Examples, but the present invention is not limited to the following Examples unless the gist of the present invention is exceeded. Examples 1 to 6 Approximately three times the amount of quinoline was added to coal tar pitch (softening point 78°C, quinoline insoluble content 4.5% by weight),
It was heated to about 90°C and dissolved. After passing this through a glass filter, the liquid was distilled under reduced pressure to remove quinoline and obtain pitch free of free carbon. Approximately 400 g of this pitch was placed in a 500 ml cylindrical glass container, melted in a furnace heated to approximately 300°C, and then heated to a specified temperature in nitrogen gas with stirring at a rate of 3°C per minute. The temperature was maintained for a predetermined time. The heat-treated pitch was crushed, and about three times the amount of quinoline was added thereto, and the mixture was heated and dissolved at about 90°C. After applying this to a centrifugal precipitator and removing the supernatant,
Fresh quinoline was added, heated, and then centrifuged. After repeating this operation 5 times, benzene was added to the precipitate, which was refluxed for about 1 hour, and then filtered through a glass filter. The filtrate was then thoroughly washed with acetone and dried to collect the quinoline-insoluble matter, which was used as carbonaceous mesophase. Table 1 shows the heat treatment temperature and time of the raw material pitch, as well as the obtained carbonaceous mesophase (30 g) and quinoline (60 g).
The mixture was placed in a 300 ml autoclave, the inside of which was purged with argon, and the mixture was heated to 440°C at a rate of 5°C per minute while stirring, and held for 60 minutes. After cooling to room temperature, the entire contents were washed out with quinoline and filtered through a glass filter. The residue was thoroughly washed with quinoline, then benzene and acetone, and then dried. This was designated as quinoline-treated mesophase. The yield of mesophase obtained by this treatment is also shown in Table 1. The carbonaceous mesophase obtained in the above manner was
Separated with ~42 Tyler mesh sieve and adjusted to particle size of 24 to 42 mesh. 800 ml of this in nitrogen gas.
After firing at ℃, it is heated to 3000℃ in a Tamman furnace.
Graphitized for 30 minutes. Approximately 3 g of the obtained graphitized material was accurately weighed, placed in a 20 ml measuring cylinder, and after filling well, the volume was measured. Next, put it in a 300 ml Erlenmeyer flask and add 30 ml of a mixed acid containing 9 parts of concentrated sulfuric acid (concentration 99.8%) and 1 part of concentrated nitric acid (concentration 64%).
After oxidizing for 60 minutes in an oil bath at 100°C, the reaction was stopped by pouring it into about 500 ml of water. After passing through a glass filter and drying at about 100°C, the volume was measured by weight and using a 20ml measuring cylinder. Repeat this operation 3 times to achieve a total temperature of 100℃ and 180℃.
Oxidized for minutes. The packing density was determined from the weight and volume, and the degree of expansion was expressed as the ratio of the filling density before and after oxidation as the apparent expansion coefficient, as shown by the following formula. Apparent expansion coefficient=packing density before oxidation treatment/packing density after oxidation treatment The obtained results are shown in Table 2. Example 7 Coal tar pitch 500 similar to Examples 1 to 6
g, anthracene oil 500g and as a catalyst
25 g of Fe ₂ O ₃ was injected into an autoclave with a volume of 2 and hydrogenated at a hydrogen pressure of 100 Kg/cm ² G at a temperature of 450° C. for 10 minutes, and then the contents were distilled under reduced pressure to obtain a hydrogenated pit. The obtained hydrogenated pitch was used in Example 3.
Heat treatment and solvent treatment were performed in the same manner as above to obtain carbonaceous mesophase as a quinoline-insoluble component. The results are shown in Table 1. The obtained carbonaceous mesophase was then subjected to graphitization treatment and wet oxidation treatment in the same manner as in Examples 1 to 6 to obtain expanded graphite of the present invention. The results are shown in Table 2. Example 8 10 g of the carbonaceous mesophase obtained in Example 3 and 20 g of tetrahydroquinoline were injected into a 300 ml autoclave and placed in an argon atmosphere under autogenous pressure.
Heat treated at 440℃ for 60 minutes (heating rate 5℃/min),
The obtained contents were filtered and washed to obtain hydrogenated carbonaceous mesophase. The amount of decrease in the concentration of tetrahydroquinoline after the heat treatment was measured, and the amount of hydrogen consumed was calculated from the amount of hydrogen in the generated gas. The results are shown in Table 3. The obtained hydrogenated carbonaceous mesophase was subjected to graphitization treatment and wet oxidation treatment in the same manner as in Examples 1 to 6 to obtain expanded graphite of the present invention. The results are shown in Table 2. Comparative Examples 1-2 Commercially available graphite materials and petroleum coke were graphitized at 3000°C for 30 minutes, each having a particle size of 24-42 mesh, and subjected to wet oxidation treatment in the same manner as in Examples 1-6. The results are shown in Table-2. As can be seen from Table 2, the expansion rate of the quinoline-treated mesophase is greater than that of the mesophase collected at about 90°C, and the one with more quinoline-soluble components removed is more effective against expansion. It can be seen that it gives

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Figure 1 is a scanning electron micrograph (200x magnification) of the cross-sectional structure of expanded graphite of the present invention, and Figure 2 is a scanning electron micrograph (400x magnification) of the cross-sectional structure of graphitized material before oxidation treatment. It is.

Claims (1)

[Claims] 1 Heat-treated raw material pitch at 350 to 500°C to obtain heat-treated pitch to generate carbonaceous mesophase,
The carbonaceous mesophase is separated and obtained by solvent-treating the heat-treated pitch using an organic solvent that does not dissolve the carbonaceous mesophase, and the obtained carbonaceous mesophase is graphitized at 2400 to 3100°C to obtain a graphitized product. 1. A method for producing expanded graphite, which comprises obtaining the following: and then subjecting the graphitized product to a wet oxidation treatment.